The invention relates to an absorbent article, intended for female users, such as a sanitary napkin or an incontinence guard, with such a shape and size that it may be substantially accommodated in the crotch region of a pair of panties and having a longitudinal direction, a transverse direction and a thickness direction, wherein the article exhibits a liquid-pervious surface, and a liquid-impervious surface, and further an absorbent core consisting of at least one absorbent body arranged between the two surfaces, and wherein a hump is arranged at the liquid-pervious surface of the article.
A common problem associated with absorbent articles of the herein intended type is leakage of body fluid past the longitudinal side edges of the article. Such leakage is of course extremely undesirable, since it entails the risk of soiling the clothing of the user. Because of the fairly insignificant extension of the article also in the longitudinal direction, it is furthermore not unusual that liquid leaks out forwards and backwards past the end edges of the article. Thereby, a particular problem is leakage backwards which usually arises in connection with the user lying down, for example during the night.
The most frequent reason for edge leakage is that the absorbent article is deformed during use, when the article is squeezed between the thighs of the user. In this way, wrinkling arises in an uncontrollable manner both in the absorbent core of the article and in its cover material.
Such wrinkling results in the formation of channels on the surface of the article, in which body fluid may seep out past the side edges. Furthermore, the compression of the article implies that the area accessible for liquid reception is reduced, whereby the risk of body fluid ending up beside the article is significant.
A further problem in connection with the previously known absorbent articles is that the side edges of the articles risk being folded in over the liquid-pervious surface of the article because of the action from the body forces which arise when the user moves about. The area accessible for liquid reception is also drastically reduced by such folding in, since only a narrow liquid-pervious region is thereby left between the inwardly-folded side edges.
One way of reducing the risk of edge leakage caused by deformation of the article during use is to provide the article with a pre-formed hump, which during use is intended to be in contact with the genitals of the user. Excreted body fluid may in this way be caught as soon as it leaves the body of the user and immediately be absorbed into the article without flowing out across the surface thereof.
Previously known absorbent articles provided with a liquid-receiving hump are, however, afflicted with a number of disadvantages.
A common way of creating a hump has been to simply build it up by arranging a larger amount of absorbent material within the area of the hump. Since the most commonly occuring absorbent material is so-called cellulose fluff pulp, such a hump, however, collapses and loses its shape when wetted. In order to achieve a hump which is sufficiently large also in a wet state, a hump consisting of cellulose fluff pulp must comprise so much absorbent material that it becomes far too high, hard and uncomfortable to wear in a dry state.
In order to solve the problem with large, hard and uncomfortable humps, it has been suggested in EP 0 339 041 that the liquid-impervious surface of the article be provided with transverse elastic members. Such elastic members impart a certain resiliency to the article if it is subjected to flattening. The elastic members, however, do not to any great extent prevent compression and undesired deformation in the transverse direction of the article.
In another publication, EP 0 419 434, it has been suggested to create a soft hump on an absorbent article by means of locking the side edges of the article at a mutual distance which is smaller than the planar distance between the side edges. Neither does this previously known article, to any appreciable extent, resist such deformation which is caused by the article being affected by pressure and shear forces during use.
In EP 0 335 252 and EP 0 335 253 it has been suggested to provide an absorbent article with a deformation element. The deformation element is affected by the transverse compressive forces between the thighs of a user. The purpose of the deformation element is that this during use should curve a portion of the article in a direction towards the body of the user. However, it is impossible to completely control, or anticipate the shape the article will adopt for each individual user. Furthermore, it is not possible to ensure the contact between the body of the user and the surface of the article, since the degree of bulging is completely determined by how much the article is compressed in a transverse direction.
Thus, there remains a need for a leakage-proof absorbent article, which has a predictable shape, both before and during use, and which maintains its shape independently of the movements of the user and of the wetting the article is subjected to.
An article designed according to the invention, of the type disclosed in the introduction, is primarily characterized in that the hump is substantially shape permanent in the transverse direction of the article both in a dry and in a wet state, and to such an extent that the hump is not deformed in the transverse direction, either temporarily or permanently, by the forces which act on the hump during use of the article.
Further variants and embodiments are evident from the following claims.
Since the article is provided with a hump which is shape permanent both in a wet and in a dry state, it is possible to predict the shape of the hump in every situation. The fact that the hump is shape permanent implies that it remains essentially unaffected in normal use and is not deformed when it is subjected to pressure and shear forces which arise in use. It is particularly important that the hump is not compressed in the transverse direction, between the thighs of the user. It is, however, in general also an advantage if the hump is substantially incompressible also in the thickness direction.
The height of the hump above the surface of the absorbent article must be adapted so that good contact between the body of the user and the hump is ensured during use. Since the hump is so hard or stiff that it is essentially unyielding to the forces it is subjected to during use it is, however, important that the hump is not so high that it presses against the body of the user and thereby causes discomfort during use. Furthermore, it is necessary to ensure that the hump does not chafe against the sensitive soft parts in the crotch of the user. Thereby, it has been found that a hump which at its highest part projects at least 5 mm from the surface of the article, but not more than 20 mm, fulfils the requirements both of good body contact and high user comfort.
A hump in accordance with the invention is relatively narrow, suitably between 2 mm and 25 mm at the base and preferably between 12 mm and 16 mm. At the top the hump is suitably between 3 mm and 10 mm wide and preferably between 4 mm and 6 mm. The hump is designed with a substantially triangular cross-section and is, consequently, wider at the base than at the top. Since the hump is comparatively narrow, it can protrude, without any discomfort to the user, slightly in between the labia pudendi of the user. Thereby, it is an advantage if the hump slightly separates the labia pudendi, since the liquid transfer from the user to the article is thus facilitated.
At the rear portion of the hump, it should have such a shape that it is in close contact with the body of the user, in the region behind the vaginal opening. Thereby, it is avoided that body fluid leaks backwards in the furrow between the buttocks of the user and leaks out from the article. As earlier mentioned, such leakage backwards is particularly embarrassing when the user is lying down. In a corresponding way, the front portion of the hump should conform to the body shape of the user in the region in front of the vaginal opening.
It is important that the body fluid which is emitted is immediately caught and absorbed into the hump. Liquid is thus prevented from collecting between the body of the user and the hump. When the user stands up or otherwise moves about, there is a risk that a gap will arise at the front portion of the hump, between the hump and the body of the user. If a large quantity of un-absorbed liquid has been trapped between the body of the user and the surface of the article, such liquid may then flow out through the gap. Such sudden liquid flows are extremely undesirable, partly because the user perceives them as unpleasant, and partly because they considerably increase the risk of leakage.
The length of the hump is furthermore of importance to the achievement of optimum contact between the hump and the body of the user. The hump should have such a shape and extend so far backwards on the article that it essentially seals against liquid flow backwards on the article. This is achieved by means of the hump being in sealing contact against the skin behind the vaginal opening of the user. A suitable length of the hump has thereby been found to be between 70 mm and 140 mm, preferably between 80 mm and 120 mm. The hump should not extend across the entire length of the article and, in particular, it is advantageuous if a portion at the front end of the article is free from the stiff, shape permanent hump. In this way, the front end may bend and conform to the curvature on the body of the user.
In order to conform to the anatomy of the user, the hump should be highest at the portion of the article which is intended to be in contact with the vaginal opening of the user. From the highest portion, the height should gradually decrease in a direction towards the end portions of the article. Thereby, the hump should extend backwards from the highest portion between 5 mm and 40 mm and preferably between 10 mm and 30 mm. In front of the highest portion, the hump should have a length of between 50 mm and 90 mm, preferably between 55 mm and 80 mm.
A raised edge barrier may advantageously be arranged at both sides of the central hump. The edge barriers increase the leakage-security of the article by serving as seals against the groin of the user. Raised edge barriers can be achieved in a number of different ways. Preferably, the edge barriers are made of the same material as the central hump and thereby have essentially the same resistance to deformation as the hump. However other types of edge barriers, such as elastic side edges, foam rubber strips, wadding, or the like, are conceivable. The edge barriers may either be purely physical barriers, or prevent liquid passage by means of absorbing body fluid.